Safing and arming system for a munition

ABSTRACT

A control apparatus comprising a safing and arming system for a munition wherein such apparatus requires only two sensors mounted about a reference axis in angularly spaced relation. The sensors are operatively connected to provide an effective arming signal for the munition only by the simultaneous provision of a signal from both sensors under conditions of sustained free fall and the sensors are incapable of providing signals simultaneously during normal handling of the munition, making it safe to handle.

United States Patent Inventor Donald A. Brahman Englewood, Ohio App].No. 868,412

Filed Oct. 22, 1969 Patented Aug. 17, I971 Assignee AVCO CorporationRichmond, Ind.

SAFING AND ARMING SYSTEM FOR A MUNITION l6 Clalma, 14 Drawing Flgs.

[1.8. CI 102/702, 102/76 Int. Cl. F421: 13/00, F4213 21/38 Field of102/702, 76, 78, 79, 80

[56] References Cited UNITED STATES PATENTS 2.5 [5,043 7/1950 Jordan102/702 3,167,018 1/1965 Brunner 102/702 3,292,537 12/1966 Goss, Jr.102/28 3,332,354 7/1967 Silvers. Jr. et al l02/76 Primary xaminer-SamuelFeinberg Attorneys-Charles M. Hogan and Eugene C. Goodale ABSTRACT: Acontrol apparatus comprising a safing and arming system for a munitionwherein such apparatus requires only two sensors mounted about areference axis in angularly spaced relation. The sensors are operativelyconnected to provide an effective arming signal for the munition only bythe simultaneous provision of a signal from both sensors underconditions of sustained free fall and the sensors are incapable ofproviding signals simultaneously during normal handling of the munition,making it safe to handle.

PATENTEUAusmsn 3599572 SHEET 1 BF 3 kL -L j 52 INVENTOR. DONALD A.BRACKMAN BYW fi m

ATTORNEYS PATENIED we I 7 an SHEET 2 8F 3 FIG-4 FIG-3 FIG-9 O W L FIG-8INVENTOR. DONALD A, BRACKMAN BY ,,1. H7

ATTORNEYS PATENIEI) M181 7 an SHEET 3 OF 3 N A RM O Wu T E NA ER r v8. WW flu T T A A D L A N O D FIG-l4 SPIN-REV] SEC.

SAFING AND ARMING SYSTEM FOR A MUNITION BACKGROUND OF THE INVENTIONMunitions, such as bombs, missiles, and the like, which are designed forrelease from aircraft must be provided with suitable safing and armingmeans to assure safety of personnel during routine handling thereof, yetthe system used to provide such safing and arming must be capable ofarming the associated munition in a reliable manner after aerial releaseof such munition.

During the free fall of a munition, there are numerous environmentsacting on such munition and its control system and such environmentsinclude relative weightlessness of components, possible spin or rotationabout a spin axis of the munition, and aerodynamic drag along such axis.However, in a so-called fin stabilized low-drag munition or bomb, theamount of drag may be less than 0.050 g., making it economicallyimpractical to use drag as a control parameter.

Weightlessness, or zero g.," is the most logical control parameter whichmay be used in a safing and arming control system for a low-dragmunition. However, previously proposed devices utilizing zero g. as acontrol parameter are unnecessarily complicated, expensive, andcomparatively unreliable.

SUMMARY This invention provides a control apparatus sensing a lowdragcondition comprising a safing and arming system for a munition whereinthe apparatus requires only two sensors mounted about a reference axisin angularly spaced apart relation and such control apparatus may beused to provide omnidirectional sensing. The sensors are operativelyconnected to provide an effective arming signal for the munition only bythe provision of signals from both sensors simultaneously underconditions of sustained free fall and the sensors are incapable ofproviding signals simultaneously during normal handling of the munition.In addition, this invention provides an improved control apparatus inwhich the sensors are positioned about a reference axis of the controlapparatus which may be spaced from the spin axis of an associatedmunition without adversely affecting the reliability of safing andarming the munition.

Other details, uses, and advantages of this invention will becomeapparent as the following description of the embodi ments thereofpresented in the accompanying drawings proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings show presentpreferred cmbodiments ofthis invention, in which FIG. I is a schematicpresentation, with certain parts shown in perspective, of one exemplaryembodiment of a control apparatus of this invention having a referenceaxis mounted coaxially with the spin or longitudinal axis of anassociated munition;

FIG. 2 is a view with parts in cross section and parts broken away takenessentially on the line 2-2 of FIG. 1',

FIG. 3 is an enlarged, fragmentary, cross-sectional view of one of thetwo identical magnetically controlled sensors illustrated in FIG. 2particularly illustrating the flat parallel end walls of such sensor;

FIG. 4 is a view taken essentially on the line 4-4 of FIG. 3',

FIG. 5 is a cross-sectional view illustrating another embodiment of amagnetically controlled sensor which has a cylindricnl housing providedwith opposed dishlike end walls which are particularly adapted to takeinto account spacing between the reference axis of a control apparatusand the spin axis ofa munition;

FIG. 6 is a cross-sectional view similar to FIG. 5 illustrating anotherembodiment of a magnetically controlled sensor which has a housingprovided with end walls having another configuration;

FIG. I is a cross-sectional view similar to FIG. 5 illustrating stillanother embodiment of a magnetically controlled sensor which has ahousing provided with still another configuration;

FIG. 8 is a schematic diagram illustrating "go" and "no go" areas ofasingle sensor, in a l g. environment, having a housing comprised of aright circular cylindrical sidewall and flat end walls which utilizes amagnet capable of exerting a 0.5 g. force on a ferromagnetic sphericalmember carried within the housing of such sensor;

FIG. 9 is a schematic presentation illustrating the effect of spin of amunition about its spin axis when the spin axis coincides with thereference axis of an associated safing and arming apparatus and when thespin axis is spaced from such reference axis;

FIG. 10 is a schematic illustration showing a pair of cooperatingsensors which are identical to the sensor illustrated in FIG. 3 withsuch sensors spaced apart to highlight that under no condition duringnormal ground handling will there be a simultaneous signal from bothsensors to thereby provide an arming or "go" signal to an associatedmunition;

FIG. II is a schematic illustration similar to FIG. 10 showing a pair ofcooperating sensors which are identical to the sensor of FIG. 5 withsuch sensors spaced 90 apart;

FIG. 12 is a schematic illustration similar to FIG. 10 showing a pair ofcooperating sensors which are identical to the sensor of FIG. 5 withsuch sensors spaced apart;

FIG. 13 is a more detailed schematic analysis of the presentation ofFIG.l2; and

FIG. 14 is a graph showing the tolerance of various types of sensors tomisalignment of the reference axis of a control apparatus in which suchsensors are used with respect to the spin axis of an associated munitionand spin of the munition about its spin axis.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Reference is now made to FIG.I of the drawings which il lustrates one exemplary embodiment of thecontrol apparatus of this invention which is designated generally by thereference numeral 20 and is suitably supported within a munition 2!which has a longitudinal or spin axis 22. The munition 21 may be amissile, bomb, or similar device having any suitable configuration andin this example of the invention will be considered as being a finstabilized low-drag bomb having a drag along its axis 22 which is toolow to be used in an economical manner as a control parameter for thecontrol or safing and arming apparatus 20 for the munition 2].

The control apparatus 20 is used for safing, i.e., assuring the munition2i is safe and will not explode, the munition during normal handling andfor arming such munition under conditions of sustained free fall. Theapparatus 20 comprises first and second magnetically controlled sensorseach designated generally by the reference numeral 24 and each capableof providing an electrical signal through an associated electrical lineeither 26 or 27 respectively to an AND electrical logic component 30.The AND component 30 operates in a manner well known in the art andrequires that an electrical signal be provided from both sensors 24simultaneously before it can provide an output signal through a line 31to another AND logic component 32 which is similar in operation tocomponent 30.

A portion of the electrical signal through the line 31 is trans mittedto a suitable time delay circuit 33 through a line 34 which thentransmits the delayed signal to the AND component 32. Any suitable timedelay may be introduced by circuit 33; however, a l-second delay isconsidered very conser' vative. It is also accepted practice to providestill another or third signal to the AND component 32 and this may be inthe form ofa separate signal through a line 35 and such signal may beprovided as long as 4 seconds after release of the munition 21 in orderto enable arming of such munition.

From the above presentation it is apparent that three signals must besimultaneously provided to the AND component 32 to have an electricaloutput therefrom and such output is then suitably amplified through apower amplifier 36 and transmitted as an arming signal through a line 37to a suitable fuze for the munition 21 during sustained free fall ofsuch munition. The use of a time delay circuit 33 and the provision of aseparate signal through a line 35 are, in essence, additional safeguardsto assure against premature arming of the munition 21; however, thisinvention is directed to a safing and arming apparatus 20 which isutilized in providing electrical output signals 26 and 27 to the ANDcomponent 30 and the operation of such apparatus is such that it isimpossible as a practical matter to provide such signals in asimultaneous manner except during free fall of the munition 21 forsustained periods of time whereby such munition may be handled withoptimum safety.

The apparatus 20 has means, in the form of a support 40, for supportingthe sensors 24 an equal distance from a reference axis 4l of theapparatus 20 and in this example of the invention such reference axiscoincides with the spin axis 22 of the munition 21 whereby the dot-dashline centrally through the munition 21 in FIG. I will also be designatedby the reference numeral 41. The support 40 is fixed to a substantiallytubular member 42 which is supported within the munition 21 in anysuitable manner and member 42 may be supported at any desired axialposition along the munition 21. The sensors 24 may be fixed to thesupport 40 using any known technique and may be angularly spaced apartbetween 90 and 180 depend ing on the configuration and positioningthereof in an associated munition. In the illustration of FIG. 1 thesensors 24 are spaced apart 90, placed an equal distance from theirreference axis 41, and supported by the support 40 in a plane arrangedperpendicular to the coinciding axes 22 and 41.

The sensor 24 is in the form of a magnetically controlled sensor andcomprises a magnetic member in the form of a spherical member orferromagnetic ball 43 which is carried within housing means comprised ofa member 44 which has a volume 45 which is greater than the volume ofthe member 43 and such volume allows unobstructed movement of the member43 within housing member 44, see FIGS. 2 and 3. The member 44illustrated in FIG. 2 of the drawings comprises a right circularcylindrical sidewall 46 and a substantially planar end wall 47 which isarranged parallel to and opposite a substantially planar wall 50comprising the housing means and in this example is formed as anintegral part of the support 40. However, the wall 50 need notnecessarily be provided as an integral part of the support 40 and may beprovided either as a separate member or as a part of housing member 44.

Electrical signal means in the form of an electrical device 51 issupported by the support 40 and the electrical device 51 includes amagnet 52 which is capable of exerting an attractive force against theball 43 which is less than the weight of such ball and for a purposewhich shall be apparent subsequently. The device 51 is a noncontactelectrical device which provides an electrical signal therefrom when theball 43 is in a centered condition essentially as illustrated for thetop sensor 24 in FIG. 2. The manner in which each sensor 24 provides anelectrical output signal through its associated line, either line 26 or27, upon centering of its associated magnetic ball 43 is well known inthe art and hence will not be described in detail. Basically, all thatis involved is that once the ball 43 is centered with respect to certainelements of the electrical device 51, magnetic and/or electrostaticfields surrounding the device 51 is altered thereby changing the effectsof the device 51 on a control device (not shown) connected thereto.

The sensors 24 are angularly spaced apart 90 about the reference axis 41and spaced an equal distance, indicated at 53, from such axis. Further,the AND logic component requires that signals be provided simultaneouslyfrom both sensors 24 in order to arm the munition 21 and this is onlypossible under conditions of sustained free fall. During ground handlingthe magnet 52 associated with each sensor 24 does not have sufficientstrength to attract its ball 43 to the required centered position andmust rely on orientation of the associated housing to help achievecentering. However, the

angular spacing of the sensors 24 assures that there is no handlingcondition where it is possible to center both balls 43 within theirassociated housings simultaneously whereby the munition 21 utilizingcontrol apparatus 20 may be handled with optimum safety.

The detailed presentation will now proceed to highlight the manner inwhich the construction and arrangement of the sensors 24 will afiect thesensitivity of the apparatus 20 during normal handling thereof andparticular reference is now made to FIG. 8 of the drawings whichillustrates a single sensor 24 having a magnet which is capable ofexerting a 0.5 g. force. The sensor is shown with its opposed parallelplanar or flat walls initially arranged horizontally and with gravityacting vertically in a direction as indicated by the arrow G. The sensor24 provides an effective output signal when it is moved through a 60 areindicated at 54 when it is arranged beneath its reference axis 41 and oneither side of the vertically acting force of gravity g. The sensor ofFIG. 8 also provides an effective output signal when it is arrangedabove the reference axis 41 and through an angle of 60 which will bedesignated by the reference numeral 55. The orientation of an associatedmunition so that a single sensor 24 would be placed in a positionbetween the angles indicated at 54 and 55 would result in such sensorbeing in areas where it would be possible for the sensor to provide anefiective electrical arming signal to the munition whereby the sensorwould be in areas popularly referred to as go" areas. The placement of asingle sensor 24 within angles 56 and 57 in FIG. 8 would result in suchsensor being in areas where it would be impossible to provide aneffective electrical arming signal from such sensor whereby the sensorwould be in areas popularly referred to as "no go" areas.

However, the improved apparatus 20 shown in FIGS. 1 and 2 uses twosensors 24 spaced 90 apart whereby it is impossible to providesimultaneous centering of the balls 43 within their associated housingmeans during normal handling and this is highlighted in FIG. 10 of thedrawings. In particular, the force of gravity acting on balls 43 isdepicted as an arrow G initially acting vertically downwardly throughthe reference axis 41. Different orientations of the control apparatus20 and hence munition 21 may be considered merely by considering theforce of gravity as acting radially outwardly in different directionsthrough 360 about axis 41 and this may be readily visualized byconsidering the shaded go" areas of FIG. 10 as remaining stationarywhile simultaneously rotating the arrow G and both sensors 24 wherebyunder no condition is it possible for both sensors 24 to provide outputsignals in a simultaneous manner therefrom. In particular. it is seenthat for every instance where one sensor is in a go" area the othersensor is at least 30 away from "go" whereby for two sensors 24 havinghousing means comprised of right circular cylindrical sidewalls andplanar end walls arranged in parallel relation the 90 separationrepresents optimum spacing to assure safe handling of the munition 21.

The utilization of only two sensors 24 spaced 90 apart enables easyinstallation of such sensors at precise positions away from thereference axis of the associated safing and arming apparatus and avoidsthe complications of attempting to install such sensors on suchreference axis and coincident with the spin axis of an associatedmunition as is required by some systems in an efi'ort to provide theassociated system with omnidirectional capabilities. Further, if anapparatus 20 could be installed so that its reference axis 41 coincidedexactly with the spin axis 22 of a munition 21 such apparatus would beeffective in arming the munition 21 during sustained free fallconditions even with the munition 2I spinning at comparatively highspeeds about its spin axis 22.

As a practical matter, there will be some spin ofa munition 21 about itsaxis 22. If the axis 41 of the control apparatus 20 coincides exactlywith the spin axis 22 the dominating force is centrifugal, asillustrated by the arrow 60 in FIG. 9, and is normal to the opposed endwalls of each sensor 24 whereby it has virtually no effect on thecentering of the associated ball 43. However, if the reference axis 41and spin axis 22 are misaligned or spaced apart by an exemplary distanceas indicated at 61 in FIG. 9 the centrifugal force 60 has a component 62which tends to move the ball 43 within the housing means of itsassociated sensor away from the center and may thereby prevent thegeneration of a valid arming signal. Obviously. this objectionablecondition may be avoided by utilizing special sensors constructed andarranged in accordance with the teachings of this invention and whichwill be described subsequently.

Reference is now made to FIGS. 5, 6, and 7 of the drawings wherein ineach Figure a sensor is illustrated which is very similar in operationand construction to the sensor 24; therefore, each sensor of FIGS. 5-7will be designated generally by the reference numeral 24 followed by adifferent letter designation for each different Figure and parts of thesensor in each Figure which are very similar to corresponding parts ofthe sensor 24 will be designated by the same reference numeral as in thesensor 24 followed by an associated letter designation and not describedagain. Only those parts of each sensor which are substantially differentfrom corresponding parts of the sensor 24 will be designated by a newreference numeral also followed by an associated letter designation anddescribed in detail. Thus, the sensors of FIGS. 5, 6, and 7 will bedesignated by the reference numerals 24A, 24B, and 24C, respectively.Further, the sensors 24A-C may be used in the control apparatus 20illustrated in FIG. 1 in lieu of the sensors In general, it will be seenthat each sensor 24A-C has housing means comprised of a right circularcylindrical sidewall and dishlike or dished end walls arranged atopposite ends of an associated cylindrical sidewall with the dishlikeend walls of a particular sensor having substantially identicalconfigurations. Further, each end wall comprising the housing means ofeach sensor 24A, 24B, and 24C is provided with an inclined peripheralportion which is preferably inclined at an angle ranging between I and12 with respect to a plane extending perpendicularly through a centralaxis of the associated cylindrical sidewall and the manner ofestablishing the degree of inclination of the peripheral portion will bedescribed in detail subsequently.

The sensor 24A is illustrated in FIG. 5 and is comprised of housingmeans or a housing 44A defined by a right circular cylindrical sidewall46A and substantially identically contoured end walls 63A and 64Aarranged at opposite ends of the cylindrical sidewall 46A with end wall64A and sidewall 46A being by way of an example made as a single member.The end wall 63A is dished or convex generally inwardly toward thecenter of the housing 44A while the end wall 64A is dished or convexgenerally outwardly from the center of such housing.

Each end wall 63A and 64A has a planar central portion of circularoutline designated in each instance by the reference numeral 65A and asubstantially frustoconical peripheral portion 66A. The electricalsignal device 51A for sensor 24A is provided in the central portion 65Aof wall 64A.

The sensor 248 is illustrated in FIG. 6 and is comprised of housingmeans or a housing 443 defined by a right circular cylindrical sidewall46B and end walls 678 and 70B of substantially identical configuration.In particular, each wall 678 and 70B is substantially arcuate as viewedin cross section and wall 708 has the electrical signal device 518 forsensor 248 provided in the central portion thereof.

The sensor 24C is illustrated in FIG. 7 and is comprised of housingmeans or a housing 44C defined by a right circuiar cylindrical sidewall46C and a pair of end walls 71C and 72C of substantially identicalconfiguration. Each end wall 71C and 72C has a substantially conicalconfiguration. The signal device 51C for sensor 24C is provided in endwall 72C adjacent its apex.

The outer portion of each end wall comprising each sensor is inclined atan angle ranging between l0 and 12 with a plane arranged perpendicularto the central axis through the associated right circular cylindricalsidewall, as previously mentioned, and this inclination tends tocompensate for the centrifugal forces tending to move the ferromagneticball of each sensor offcenter due to the utilization of sensors as partof a control apparatus which has its reference axis spaced apart fromthe spin axis of an associated munition. In particular, for each wall63A and 64A of sensor 24A frustoconical portion 66A has a correspondingfrustoconical inside surface which is inclined between l0"l2 relative tothe inside planar surface of planar portion 65A (which is parallel tothe above-mentioned perpendicular plane), each arcuate wall 67 B and 70Bof sensor 24B has a corresponding arcuate inside surface which isgenerally inclined between l0l2 relative to such perpendicular plane,and each conical wall 71C and 72C of sensor 24C has a correspondingconical inside surface which is inclined between 10 l 2". The incliningof at least the peripheral portion of each end wall between 10 and 12has been determined based upon angularly spacing a pair of identicalsensors (whether sensor 24A, 248, or 24C) between 90 and 100 and witheach sensor of a cooperating pair positioned an equal distance from thereference axis of its associated control apparatus. Further, each sensorwhether sensor 24, 24A, 24B, or 24C is arranged so that a radial linefrom the reference axis coincides with the central axis for its rightcircular cylindrical sidewall.

The above presentation explains how the sensors may be physicallyaltered to compensate for spin effects when the axis of the munition andthe axis of the safing and arming apparatus are spaced apart. However,this physical alteration must be examined to determine its effect duringnormal han dling ofthe munition.

Accordingly, reference is now made to FIG. ll of the drawings whichillustrates a pair of cooperating sensors 24A wherein the force ofgravity is shown acting in the direction indicated by the arrow G andeach magnet comprising each sensor 24A is capable of exerting a force of0.5 g. The schematic presentation of FIG. II is similar to thepresentation of FIG. It]; however, FIG. II has cross-hatched areasinstead of shaded areas which are considered go areas for one sensor 24Aand white for the other while shaded areas represent transition areas.

A typical control apparatus such as apparatus 20 would use a pair ofsensors 24A mounted 90 apart in the manner illustrated in FIG. I]. Inthis exemplary presentation the inside surfaces of the peripheralportions of end walls 63A and 64A are shown inclined at [2 which adds tothe sensitive area on each side of vertical, for example, and this isdue to the fact that the force component along each angled l2 surface isnot greater than 0.5 g., or at 30 to the horizon, until the sensorcentral line moves through an angle of 42 on either side of vertical.

For a detailed understanding of FIG. ll consider the force of gravity asan arrow G acting downwardly through the lower sensor 24A. Rotating bothsensors 24A coupled thereto counterclockwise moves the lower sensor 24Aout of the right 42 "go area 73 into the 6 shaded area 74. At this pointthe upper sensor 24A is moving into the 1 3 shaded area 75 and is l8away from the cross-hatched or go area 76 whereby there is an 18 safetymargin.

In rotating the sensors 24A clockwise, as the lower sensor 24A reachesthe closest line of the shaded area 77 the uppe. sensor 24A is within 6of the area 74 which is considered a critical area because when gravityis acting in area 74 each sensor would be within 3 of a go" condition.Nevertheless, the shaded areas 74, 75. 77, and 80 are transition areas nt go areas between both sensors being go. Thus, it is seen that duringnormal handling of a munition having a control system which uses a pairof sensors 24A spaced there is no condition where both sensors 24A wouldprovide a go" signal whereby the associated control system would beconsidered safe. It will also be apparent from FIG. 11 that increasingthe angle of inclination of the inside surfaces of opposed end walls ofeach sensor 24A to an amount greater than 12 would reduce the safety or"no go" areas and hence would not be considered practical.

The margin of safety may be increased by increasing the distance betweena pair of sensors such as sensors 24A and this will be discussed inconnection with FIG. 12 of the drawings where the angle of separationbetween sensors 24A is increased from 90 to l.

In considering the presentation of FIG. 12 is will be seen that theshaded transition area 82 is not critical since it extends through anangle of 16". However, two shaded transition 8 areas indicated at 83 and84 require further analysis and for this analysis reference is also madeto FIG. 13 of the drawings. When gravity is acting as indicated by thearrow G in FIG. 13 the bottom sensor 24A is 8 away from a go conditionas indicated at 85. However, in the top sensor 24A it will be seen thatthe magnet surface is 30 away from a horizontal condition as indicatedat 86 while the ball within the member 24A is resting against a surfaceat 42 to the horizontal plane as in dicated at 87: therefore, in thiscondition the top sensor must move another l2 to a cross-hatched or "go"area whereby the 8 safety ranges are effectively 20 from "no go" to go,"i.e., 8 plus IT. From the above, it is seen that the l00 separationprovides maximum safety.

In considering static and fractional G conditions, for exam ple, if thedish angle or inclination of the outer portions of the end walls foreach sensor were IS, the 42 angles will be increased to 45 each. Then,in the 100 separation, the two 8 ranges decrease to each and the l6angle reduces to l0, whereby any efi'ort to increase the most criticalarea back toward l6 by increased separation would reduce each of the 5areas equally toward zero. This highlights that in using sensors 24A,24B, and 24C, and which have magnets which exert a 0.5 g. force, thereshould be no attempt to provide increased angular separation between apair of cooperating sensors to angles greater than l00.

As previously indicated, it is impractical to attempt to place a safingand arming apparatus within an associated munition with its referenceaxis 41 coinciding exactly with the spin axis 22 of the munition. Thus,in case of a fin stabilized low-drag munition when zero g. sensors areutilized, it is much more realistic to design the sensors so as tooffset the detrimental effect of centrifugal forces acting against eachsensor and tend ing to move from center its associated ball. Thisinvention provides three sensors 24A, 24B, and 24C which enablecomparatively great misalignment of axes 22 and 41 without adverselyaffecting the reliability of the safing and arming system.

Reference is now made to FIG. 14 which presents four curves to highlightthat by providing sensors having dishlike end walls essentially as shownfor the sensors 24A, 24B, and 24C and wherein a cooperating pair of eachtype of sensor are installed essentially as shown in FIG. 2, greatermisalignment of the reference axis may be tolerated relative to the spinaxis of an associated munition. In particular, it will be seen that eachcurve is a plot of distance of misalignment ofa reference axis of acontrol apparatus from a spin axis of an associated munition versus spinabout such spin axis in revolutions per second.

Curve 90 is for sensor 24 having its ball initially displaced 0.1 inchfrom center, curve 91 is for sensor 24 having its ball initially oncenter, curve 92 is for sensor 24A with its ball initially displaced 0.1inch from center, and curve 93 is for sensor 24C with its ball locatedcentrally. From these curves it is apparent that a greater displacementof the reference axis ofa control system from the spin axis of amunition is possible using sensors having dishlike end walls of thecharacter illustrated in FIGS. 5-7 of the drawings. Further, and asprevi ously described in detail it will be apparent that a controlsystem utilizing sensors 24A-C provides adequate safety during normalground handling.

Thus, it is seen that this invention enables the utilization of only twomagnetically controlled sensors in a control apparatus or system of thecharacter described which are spaced from the reference axis of suchcontrol apparatus. Further, the two sensors may be spaced apart between90 and 100, depending on the detailed configuration thereof. A pair ofsensors 24 are preferably spaced apart 90 while a pair of sensors 24A,24B, and 24C may be spaced apart between and yet an associated safingand arming, i.e., control, apparatus using a cooperating pair of suchsensors provides optimum safety during normal handling and providesreliable arming of the associated munition during sustained free fallwhile taking into account centrifugal forces acting on the controlapparatus.

In this disclosure of the invention each electrical signal device 51A,51B, and 51C of sensors 24A, 24B, and 24C, respectively, is shownprovided in an associated end wall, However, it will be appreciated thatthe signal device may merely associate with a particular end wallwithout being provided therein.

While present exemplary embodiments of this invention, and methods ofpracticing the same, have been illustrated and described, it will berecognized that this invention may be otherwise variously embodied andpracticed by those skilled in the art.

What I claim is:

I. A control apparatus having a reference axis and comprising, a firstsensor capable of providing a first electrical signal, a second sensorcapable of providing a second electrical signal, and means supportingsaid sensors an equal distance from said reference axis and in angularlyspaced apart relation, said sensors being operatively connected toprovide an effective arming control signal only by the simultaneousprovision of said first and second signals under conditions of sustainedfree fall and said sensors being incapable of providing said controlsignal during normal handling of said apparatus.

2. An apparatus as set forth in claim I in which said supporting meanssupports said sensors in a plane arranged perpendicular to saidreference axis.

3. An apparatus as set forth in claim I in which said sensors areangularly spaced apart between 90 and ISO.

4. An apparatus as set forth in claim I in which each of said sensorscomprises, a magnetic member, housing means for containing said magneticmember, said housing means having a volume which is greater than thevolume ofsaid member and thereby allowing unobstructed movement of saidmember within said housing means, electrical signal means carried bysaid housing means and providing an associated electrical signal uponsaid member in operative association therewith, and a magnet for movingsaid member into said operative association, said magnet an attractiveforce against said member which is less than the weight of said memberso that magnetic force from said magnet alone is effective in causingthe provision of said associated electrical signal only under saidconditions of sustained free fall.

5. An apparatus as set forth in claim 4 in which said member comprises asubstantially spherical member and said housing means comprises asubstantially right circular cylindrical sidewall having an effectiveheight which is larger than the diameter of said spherical member.

6. In combination: a munition having a spin axis and an apparatus forsaflng said munition during normal handling and arming said munitionunder conditions of sustained free fall, said apparatus having areference axis and being supported by said munition and comprising, afirst sensor capable of providing a first electrical signal, a secondsensor capable of provid ing a second electrical signal, and meanssupporting said ser1- sors an equal distance from said reference axisand in angularly spaced apart relation, said sensors being operativelyconnected to provide an effective arming signal to said mun tion only bythe simultaneous provision of said first and second signals underconditions of sustained free fall and said sensors being incapable ofproviding said first and second signals simultaneously during normalhandling of said munition making it safe to handle.

7. A combination as set forth in claim 6 in which said sensors areangularly spaced apart between 90 and 8. A combination as set forth inclaim 6 in which said supporting means supports said sensors in a planearranged perpendicular to said reference axis.

9. A combination as set forth in claim 6 in which each of said sensorsis magnetically controlled and comprises a magnetic member, housingmeans for containing said magnetic member, said housing means having avolume which is greater than the volume of said member and therebyallowing unobstructed movement of said member within said housing means,electrical signal means carried by said housing means and providing anassociated electrical signal upon moving said member in operativeassociation therewith, and a magnet for moving said member into saidoperative association, said magnet exerting an attractive force againstsaid member which is less than the weight of said member so thatmagnetic force from said magnet alone is effective in causing theprovision of said associated electrical signal only under saidconditions of sustained free fall.

10. A combination as set forth in claim 9 in which said member comprisesa spherical member and said housing means comprises a substantiallyright circular cylindrical sidewall having an effective height which islarger than the diameter of said spherical member.

ll. A combination as set forth in claim 9 in which said reference axisis spaced from said spin axis due to routine mounting of said apparatuswithin said munition and said housing means comprising each sensorcomprises a cylindrical sidewall and a pair of dishlike end wallsarranged at opposite ends of said cylindrical wall, one of said pair ofwalls having a surface which is convex inwardly toward the center of itssensor and the other of said walls having a cooperating surface which isconcave inwardly toward said center, said housing means being fixed tosaid supporting means with a central axis through said cylindricalsidewall coinciding with a radial line arranged perpendicular to saidreference axis and with said surface in said other wall being concaveinwardly toward said reference axis, said surfaces serving to minimizethe effect of centrifugal forces acting upon said sensors due to thespacing between said reference axis and said spin axis.

12. A combination as set forth in claim 11 in which said sensors areangularly spaced apart between and and each of said surfaces has aninclined peripheral portion which is inclined at an angle rangingbetween 10 and 12 with respect to a plane arranged perpendicular to saidradial line.

13. A combination as set forth in claim ll in which each of saidsurfaces is substantially arcua as viewed in cross section.

14. A combination as set forth in claim ii in which each of saidsurfaces comprises a planar central portion of circular outline adjoinedby a substantially frustoconical peripheral portion,

15. A combination as set forth in claim 11 in which each of saidsurfaces is substantially conical.

16. A combination as set forth in claim 9 in which each of said sensorsis sensitive in a plurality of directions in an associated plane andsaid supporting means supports said sensors with the associated planesof each sensor arranged per pendicular to each other to effectivelyprovide an omnidirectional sensing system using only said first andsecond sensors

1. A control apparatus having a reference axis and comprising, a firstsensor capable of providing a first electrical signal, a second sensorcapable of providing a second electrical signal, and means supportingsaid sensors an equal distance from said reference axis and in angularlyspaced apart relation, said sensors being operatively connected toprovide an effective arming control signal only by the simultaneousprovision of said first and second signals under conditions of sustainedfree fall and said sensors being incapable of providing said controlsignal during normal handling of said apparatus.
 2. An apparatus as setforth in claim 1 in which said supporting means supports said sensors ina plane arranged perpendicular to said reference axis.
 3. An apparatusas set forth in claim 1 in which said sensors are angularly spaced apartbetween 90* and 180*.
 4. An apparatus as set forth in claim 1 in whicheach of said sensors comprises, a magnetic member, housing means forcontaining said magnetic member, said housing means having a volumewhich is greater than the volume of said member and thereby allowingunobstructed movement of said member within said housing means,electrical signal means carried by said housing means and providing anassociated electrical signal upon said member in operative associationtherewith, and a magnet for moving said member into said operativeassociation, said magnet an attractive force against said member whichis less than the weight of said member so that magnetic force from saidmagnet alone is effective in causing the provision of said associatedelectrical signal only under said conditions of sustained free fall. 5.An apparatus as set forth in claim 4 in which said member comprises asubstantially spherical member and said housing means comprises asubstantially right circular cylindrical sidewall having an effectiveheight which is larger than the diameter of said spherical member.
 6. Incombination: a munition having a spin axis and an apparatus for safingsaid munition during normal handling and arming said munition underconditions of sustained free fall, said apparatus having a referenceaxis and being supported by said munition and comprising, a first sensorcapable of providing a first electrical signal, a second sensor capableof providing a second electrical signal, and means supporting saidsensors an equal distance from said reference axis and in angularlyspaced apart relation, said sensors being operatively connected toprovide an effective arming signal to said munition only by thesimultaneous provision of said first and second signals under conditionsof sustained free fall and said sensors being incapable of providingsaid first and second signals simultaneously during normal handling ofsaid munition making it safe to handle.
 7. A combination as set forth inclaim 6 in which said sensors are angularly spaced apart between 90* and180*.
 8. A combination as set forth in claim 6 in which said supportingmeans supports said sensors in a plane arranged perpendicular to saidreference axis.
 9. A combination as set forth in claim 6 in which eachof said sensors is magnetically controlled and comprises a magneticmember, housing means for containing said magnetic member, said housingmeans having a volume which is greater than the volume of said memberand thereby allowing unobstructed movement of said member within saidhousing means, electrical signal means carried by said housing means andproviding an associated electrical signal upon moving said member inoperative association therewith, and a magnet for moving said memberinto said operative association, said magnet exerting an attractiveforce against said member which is less than the weight of said memberso that magnetic force from said magnet alone is effective in causingthe provision of said associated electrical signal only under saidconditions of sustained free fall.
 10. A combination as set forth inclaim 9 in which said member comprises a spherical member and saidhousing means comprises a substantially right circular cylindricalsidewall having an effective height which is larger than the diameter ofsaid spherical member.
 11. A combination as set forth in claim 9 inwhich said reference axis is spaced from said spin axis due to routinemounting of said apparatus within said munition and said housing meanscomprising each sensor comprises a cylindrical sidewall and a pair ofdishlike end walls arranged at opposite ends of said cylindrical wall,one of said pair of walls having a surface which is convex inwardlytoward the center of its sensor and the other of said walls having acooperating surface which is concave inwardly toward said center, saidhousing means being fixed to said supporting means with a central axisthrough said cylindrical sidewall coinciding with a radial line arrangedperpendicular to said reference axis and with said surface in said otherwall being concave inwardly toward said reference axis, said surfacesserving to minimize the effect of centrifugal forces acting upon saidsensors due to the spacing between said reference axis and said spinaxis.
 12. A combination as set forth in claim 11 in which said sensorsare angularly spaced apart between 90* and 100* and each of saidsurfaces has an inclined peripheral portion which is inclined at anangle ranging between 10* and 12* with respect to a plane arrangedperpendicular to said radial line.
 13. A combination as set forth inclaim 11 in which each of said surfaces is substantially arcuate asviewed in cross section.
 14. A combination as set forth in claim 11 inwhich each of said surfaces comprises a planar central portion ofcircular outline adjoined by a substantially frustoconical peripheralportion.
 15. A combination as set forth in claim 11 in which each ofsaid surfaces is substantially conical.
 16. A combination as set forthin claim 9 in which each of said sensors is sensitive in a plurality ofdirections in an associated plane and said supporting means supportssaid sensors with the associated planes of each sensor arrangedperpendicular to each other to effectively provide an omnidirectionalsensing system using only said first and second sensors.